


For Science

by supernatural9917



Series: Destiel Smut Bingo 2018 [24]
Category: Supernatural
Genre: Accidental Voyeurism, Destiel Smut Bingo 2018, Exhibitionist Dean Winchester, M/M, Science, Scientist Castiel, for science, that's a little bit on purpose
Language: English
Status: Completed
Published: 2019-02-09
Updated: 2019-02-09
Packaged: 2019-10-24 19:19:01
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,204
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17710058
Author URL: https://archiveofourown.org/users/supernatural9917/pseuds/supernatural9917
Summary: Dean signs up to take part in a science experiment studying brain activity during arousal and orgasm. Jerking off to porn for money? Sounds like his dream job! Things get a little more complicated when the person running the study turns out to be his secret crush, Cas.Written for the Destiel Smut Bingo 2018. Square filled: For science.





	For Science

**Author's Note:**

> My nether regions may still be quivering over Cas in a labcoat. I'm only human.
> 
> Potential questionable consent, see end note if you need more detail.

'…and of course, at the end of the study you'll be paid $350.' The student- Haley? Hannah? something like that- finishes her spiel and looks at Dean expectantly.

'So all I have to do is lie in the machine and jerk off, and you'll give me $350?' he asks incredulously- there must be a catch, it's too easy.

'That's correct. I mean, technically you have to do it five times with different types of stimuli, so it will take multiple visits. We have a sign-up sheet so you can choose your time slots.'

'What kind of stimuli?'

The girl- Hannah, he's pretty sure- tucks her long brown hair behind her ear and reads from a list. 'Heterosexual sex, homosexual female sex, homosexual male sex, and mixed group sex.' She somehow manages not to blush, but that's OK, because Dean is blushing enough for both of them.

'So, like, are they gonna be in there with me, or…'

'Oh no!' Hannah interrupts. 'You'll be watching pornography featuring these stimuli. We'll measure your brain activity with the fMRI while you watch and try to bring yourself to orgasm.'

Well, that he can do. If only he could turn jerking off to porn into a full-time job, he'd be rich as hell. 'Cool, sign me up.'

'Great!' she says enthusiastically. 'I just need you to fill out the intake form, and then the sign-up sheet for your sessions.'

Dean takes the form, which has the usual disclaimers and questions, but one question stops him short. 'Why do you need to know my sexuality?' he asks defensively.

'It's a study about brain activity during sexual arousal and orgasm,' Hannah explains matter-of-factly. 'We need to know your sexuality so we can make statistical comparisons among groups. All of the information stays completely confidential.'

'Oh. OK.' Dean picks up the pen and answers all the other questions first. When he gets to the sexuality question, he takes a deep breath before circling the word bisexual. He feels a strange sense of relief doing it, finally admitting it to someone other than himself- even if it is just to a piece of paper that will only be seen by a couple of neuroscience grad students. He hands the form back to Hannah, and her eyes light up.

'Oh, wonderful! We've struggled to recruit bisexual participants. Now I just want to assure you again, all of your details will be anonymised in the system, and the person who performs the fMRI will not be involved in the analysis of the data.'

'Cool, whatever. When can I start?' Dean asks, eager to finish this thing and get paid.

'Here's the sign-up sheet,' Hannah says, handing him a printed-out spreadsheet. He picks five slots within the first week of the study and is sent on his way with an appointment reminder card containing his study ID number, which is how the people running the study will know him in order to preserve his privacy.

His first appointment is two days later, and he arrives fifteen minutes early as requested. He's sitting in the waiting area for less than five minutes when he hears a familiar voice.

A guy wearing scrubs and a lab coat walks out reading a file, and without looking up calls out, 'Number 24601?'  

Shit shit shit. It's Cas. It's Cas fucking Novak, and he's dressed like Dr Sexy minus the cowboy boots, and he's going to watch Dean jerk off in an MRI machine, except Dean might just cream himself right now instead. Cas finally looks up, and his eyes widen when he sees Dean.

'Dean! Are… are you 24601?'

'Uh. Yeah.' He pulls out his appointment card and shows it to Cas.

Cas swallows hard, a blush suffusing his cheeks. He looks at the file again, and oh shit, Dean realises that his answers to the intake form must be in there. Well, looks like he's just kind of come out to Cas.

'So, um, I just need to confirm your details first,' Cas says, sounding nervous as he indicates the room he came out of for them to talk. Dean nods and walks in, Cas following behind and closing the door. He confirms Dean's date of birth, ethnicity, religious affiliation, and consents before circling back to the all-important question. 'And, um, it says that you identify as, um, bisexual?'

Dean would tease Cas about blushing if he wasn't aware that he was blushing even more. 'Uh, yeah. Is that… OK?'

'It's great!' Cas says enthusiastically, then seems to remember himself, 'I mean, for the study. We've struggled to recruit bisexual participants.'

Dean tries not to feel too disappointed that that's the reason for Cas's excitement about his sexuality. 'Hannah said the same thing. So, how does this work, do I get naked, or…' he trails off, seeing Cas's eyes widen again.

'Oh! Y-yes, there's a hospital gown for you in the MRI room, just put it on with the opening in the front.' He fidgets with the file then looks up at Dean again. 'I can find someone else to run the scan if you want. I understand this may be awkward since we're friends.'

Dean can't hide his surprise; as far as he knew, Cas sees him as a friendly acquaintance within overlapping circles of friends, and Dean sees Cas as the unrequited crush of his closeted dreams. Hearing that Cas sees them as friends makes him feel a bit warm inside, and gives him a bit of confidence too. 'I mean, I don't mind, it's for science, right? But if you don't want to watch me spankin' it, I get it.'

'I didn't say that,' Cas replies quickly, blush deepening further. 'I mean, I'm not saying… I wouldn't be watching you… the… process as such, I'd be watching the MRI. We can put up a privacy screen so I can't see your lower half.'

'Cool, well, I'm OK with it if you're OK with it,' Dean shrugs, brilliantly performing a nonchalance he isn't even close to feeling.

'OK. If you want to go in then, I'll set everything up in the control room.' He hurries off to said control room, and Dean goes into the MRI room. Behind the privacy screen, there's a chair with a hospital gown on it, and Dean takes off his clothes and changes into it. Careful to keep it closed, he wanders over to the MRI machine and waits for Cas. 'Hello, Dean. Everything OK?' comes a voice over an intercom, and Dean looks over at the window where a still-blushing Cas is waving.

'Yeah, I'm cool. Do I just hop in?'

'Yes, just lie on your back and scoot backwards until your head is in the headrest and you can see the screen.'

Dean looks at the privacy screen but decides not to bother moving it. Hell, maybe if he's lucky, Cas will sneak a peek and like what he sees. He climbs up as instructed, and once he's in position, he tells Cas he's ready.

'Do you have a preference of which stimulus you would like today?' Cas asks. 'You can choose between a heterosexual couple, a lesbian couple, a gay couple, or a mixed gender group.'

Dean considers his options and figures the cat's out of the bag now, so no point being coy about it. 'I'll take the dudes. The gay one.'

'OK, I'll get that queued up for you. You'll find lubricant and wet wipes next to you. Let me know if you get uncomfortable at any point and we can stop.'

'Thanks. I'm good.' The video starts up, and it's clear that they've picked the quality stuff for this. Production values are high, the acting isn't half bad, the dudes are hot as fuck, and the sex is even hotter. Dean reaches for the lube within ten seconds of a dick going into a mouth, and he opens the gown to grab his dick. He's so into it that he almost doesn't catch the sound, but then there's a gasp that didn't come from him or the video. He listens carefully for it again, and sure enough, another little hitched breath, a quiet moaning sigh, and… yeah, either he could hear his own fapping in stereo, or somebody else is joining in on the fun. It has to be Cas. He's the only one around from the study, the only one who would be allowed in the control room.

Cas is getting off to watching _him_ get off from gay porn.

Dean takes his hand off his dick and takes a deep breath. 'Hey, Cas?' he says, and hears a muttered curse that's probably Cas realising his microphone was still on.

'Um, yes, Dean?'

'Enjoying the show?'

'I… what?' Cas asks, sounding horrified.

'You left your mic on, buddy,' Dean says lightly, trying to convey that he isn't mad.

'Oh god, Dean, I'm so sorry, this is so unprofessional, unethical- I'll remove myself from the study immediately, and if you'd like to file a complaint or call campus police, I'll understand comp-'

'I liked it,' Dean interrupts him. 'I like you watching.' He takes his dick in hand again and starts stroking slowly. 'I liked hearing you get turned on by me. I'm watching this porno right now, and I'm picturing us doing what they're doing. They're sixty-nineing right now, Cas. Would you wanna do that with me?'

'Yes,' Cas replies breathlessly. 'Very much.'

'Good. I've never had a dick in my mouth, though. You think you could teach me how to do it right?' Holy shit, this is turning into some kind of weird phone sex, but Dean is loving it.

There's a little whimper through the intercom, and it sounds like Cas is touching himself again too. 'Yes, Dean.'

'That's good. Do you like sucking dick, Cas?'

'I love it,' Cas admits, and it's Dean's turn to moan. 'I don't have a very strong gag reflex. I can take you all the way down my throat.'

'Fuck, that's hot,' Dean replies, his hand speeding up. 'The guys are fucking now. The top is sliding in nice and slow, and the bottom loves it. Do you like being fucked, Cas?'

'I do.'

'Would you let me fuck you?'

'I would.' No hesitation. He means it, and oh, does Dean want it.

Then he asks the question he _really_ wants the answer to. 'Would you wanna fuck me?'

The reply comes in the form of a drawn-out moan, and Dean realises that Cas is coming. He's coming to the thought of fucking Dean, and son of a bitch, that makes Dean come so fucking hard that his toes go a bit numb and his peripheral vision goes black for a second.

'Was it good for you?' Dean asks cheerfully as he wipes himself down.

'Dean,' Cas says, and something in his voice makes Dean smile disappear. 'Dean, I'm so sorry, I was completely inappropriate, how could I-'

'Hey, stop that,' Dean says, scooting his way out of the MRI. Pulling his gown shut, he walks over to the window and sees Cas sitting there, clearly having cleaned himself up already, looking pale and distraught. Dean knocks on the glass to get his attention, and when Cas looks up, Dean curls his finger to indicate that Cas should come into the MRI room. Cas nods, his eyes downcast, and a minute later he comes in.

'Dean, I can only apologise again, I shouldn't even have looked-' but again Dean stops him.

'I wanted you to look. Didn't put up the screen on purpose.' Dean savours Cas's reaction, the rising blush, the wide eyes, the way he bites his lip.

'Why?'

'I mean, have you looked in a mirror lately?' Dean jokes. 'And the Dr Sexy vibe you've got going on right now is just… mmm.'

'You're attracted to me?' Cas asks, seemingly awestruck that Dean could be interested in him.

'I finally admitted to myself that I was bi when I saw you doing yoga in the quad that one time,' Dean admits. 'Does that answer your question?'

'Dean,' Cas says, voice dropping lower and eyes darkening, 'I'm also very attracted to you.'

He can't help but smirk. 'Yeah, got that impression.'

'Of course, you've ruined today's experiment.'

Dean's face drops. 'What?'

'The data was supposed to come from your reaction to the porn, but I think we can safely assume that was only a very minor part of it.'

'Shit, man, I'm sorry. I just kinda lost it when I heard you.'

'I've had much less pleasurable reasons to have to discard data,' Cas replies. 'Would you be willing to come back an extra day? We can't pay you any more than the set amount, but perhaps I can show you my appreciation another way?'

'Hell, Cas, that sounds like the start of almost every porno I've ever watched.'

Cas steps forward until he's right in Dean's personal space. 'That _is_ the intention, yes.'

That makes Dean grin widely. 'Happy to come back. For science.' He grabs Cas by the lapels of his lab coat, and Cas cuts right to the chase, grabbing Dean's ass with both hands as he nods his agreement.

'For science.'

**Author's Note:**

> Cas watches Dean masturbate, Dean notices, and Cas feels very guilty for what he sees as a violation of Dean's trust. However, as Dean is kind being an exhibitionist in the hopes of catching Cas's eyes, he is not remotely upset about it and reassures Cas that his reaction was even better than Dean had hoped.


End file.
